BEIJING (AP) -- The Chinese crested tern, a rare sea bird whose eggs are prized by some as a delicacy, is likely to be extinct in five years if authorities do not step up protection efforts, a conservation group said Friday.

The bird looks set to be the latest ecological victim of China's rapid 30-year economic expansion and industrialization, which has raised the standard of living for hundreds of millions of Chinese but ravaged the environment. Late last year, scientists declared that a rare Chinese river dolphin was effectively extinct after conducting a fruitless six-week search for the creature in its Yangtze River habitat.

A survey by a team of Chinese experts conducted over recent successive breeding seasons found that the number of crested terns had fallen to 50 birds, about half the population found three years ago, said a statement from BirdLife International, a conservation group based in Cambridge, England.

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"Without urgent action conservationists have given the bird less than five years before disappearing completely from its two remaining breeding areas," the statement said.

It quoted head of the Chinese survey team Chen Shuihua as saying the bird was "on the verge of extinction."

The biggest threat to the birds was the collection of eggs by local fisherman in the bird's breeding areas, the Jiushan islands and Matsu island off China's east coast, the statement quoted Chen, a researcher from the Zhejiang Museum of Natural History, as saying.

The tern eggs, which locals believe are more nutritious than poultry eggs, were found at sidewalk snack booths in the Chinese coastal provinces of Zhejiang and Fujian for about $5 each and also in markets in Matsu, which is controlled by Taiwan, the statement said.

Authorities need to stop the collection and sale of the eggs, step up monitoring of the birds and do more to protect their breeding habitats, it said.

The baiji, or white flag dolphin, survived for millions of years but was declared extinct in December. Around 400 baiji were believed to be living in the Yangtze in the early 1980s, but their survival was made impossible by dramatic increases in ship traffic, overfishing and the degradation of their habitat.